In building a steam or hot air distributor which consists of a main distributor pipe or chamber with many pipes out of the chamber, there are many difficulties presented by differential thermal expansion between the main steam distributor and the vessel or chamber into which the individual pipes feed. This type of system normally consists of a main steam chamber with pipes fed through a valve and some type of an expansion joint between the main steam distributor and the vessel being fed through the valve.
In the paper industry, it has been a practice to provide steam distributor over drying components on the Fourdrinier paper machine and in the press section. The steam is blown down on top of the sheet and through the sheet to improve drying. Normally, there is a vacuum device under the steam distributor on the other side of the paper or pulp mat. This is normal but not necessary. In most drying operations, it is difficult to get a uniform moisture profile across the sheet of paper or pulp. This non-uniformity causes many problems in the industry and it is desirable to have a method of correcting discrepancies in the moisture profile. Our invention consists of a multi-chambered steam distributor with separate steam flow control to each of these chambers. In the past, this has been accomplished to some extent using various normal means of connecting pipes and valves to feed steam into various areas. My invention consists of a multi-chambered steam hood with the means of steam distribution to each chamber provided by a steam distributor which has the flow control as an integral part of the distributor rather than as a separate piping system.
Steam flows from the pressurized steam distributor through port holes in the chamber nozzle into each profile chamber. The flow is controlled from zero to 100% by raising or lowering the control plug. This raising or lowering action can be actuated with any device, such as an air cylinder, an air or hydraulic diaphragm, or an electrical means. Flow control could also be obtained in a rotary motion by having holes in the plug which would line up with holes in the chamber nozzle. The heating gas need not necessarily be steam but could be any other hot gas.
In order to correct moisture distribution in most paper products, it is desirable to automatically control the cross machine moisture content using a steam shower as described above. Most machines have continuous moisture scanners which read the sheet moisture content across the machine as the paper is manufactured. The information from this continuous measurement can be fed into a controlling computer or analog computer and the steam flow can be automatically controlled according to this information.